text: #
  # Licensed to the Apache Software Foundation (ASF) under one or more
  # contributor license agreements.  See the NOTICE file distributed with
  # this work for additional information regarding copyright ownership.
  # The ASF licenses this file to You under the Apache License, Version 2.0
  # (the "License"); you may not use this file except in compliance with
  # the License.  You may obtain a copy of the License at
  #
  #    http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  #
  
  """Utility methods for testing
  
  For internal use only; no backwards-compatibility guarantees.
  """
  
  import hashlib
  import imp
  import os
  import shutil
  import tempfile
  
  from mock import Mock
  from mock import patch
  
  from apache_beam.io.filesystems import FileSystems
  from apache_beam.utils import retry
  
  DEFAULT_HASHING_ALG = 'sha1'
  
  
  class TempDir(object):
    """Context Manager to create and clean-up a temporary directory."""
  
    def __init__(self):
      self._tempdir = tempfile.mkdtemp()
  
    def __enter__(self):
      return self
  
    def __exit__(self, *args):
      if os.path.exists(self._tempdir):
        shutil.rmtree(self._tempdir)
  
    def get_path(self):
      """Returns the path to the temporary directory."""
      return self._tempdir
  
    def create_temp_file(self, suffix='', lines=None):
      """Creates a temporary file in the temporary directory.
  
      Args:
        suffix (str): The filename suffix of the temporary file (e.g. '.txt')
        lines (List[str]): A list of lines that will be written to the temporary
          file.
      Returns:
        The name of the temporary file created.
      """
      with tempfile.NamedTemporaryFile(
          delete=False, dir=self._tempdir, suffix=suffix) as f:
        if lines:
          for line in lines:
            f.write(line)
  
        return f.name
  
  
  def compute_hash(content, hashing_alg=DEFAULT_HASHING_ALG):
    """Compute a hash value from a list of string."""
    content.sort()
    m = hashlib.new(hashing_alg)
    for elem in content:
      m.update(str(elem))
    return m.hexdigest()
  
  
  def patch_retry(testcase, module):
    """A function to patch retry module to use mock clock and logger.
  
    Clock and logger that defined in retry decorator will be replaced in test
    in order to skip sleep phase when retry happens.
  
    Args:
      testcase: An instance of unittest.TestCase that calls this function to
        patch retry module.
      module: The module that uses retry and need to be replaced with mock
        clock and logger in test.
    """
    real_retry_with_exponential_backoff = retry.with_exponential_backoff
  
    def patched_retry_with_exponential_backoff(num_retries, retry_filter):
      """A patch for retry decorator to use a mock dummy clock and logger."""
      return real_retry_with_exponential_backoff(
          num_retries=num_retries, retry_filter=retry_filter, logger=Mock(),
          clock=Mock())
  
    patch.object(retry, 'with_exponential_backoff',
                 side_effect=patched_retry_with_exponential_backoff).start()
  
    # Reload module after patching.
    imp.reload(module)
  
    def remove_patches():
      patch.stopall()
      # Reload module again after removing patch.
      imp.reload(module)
  
    testcase.addCleanup(remove_patches)
  
  
  @retry.with_exponential_backoff(
      num_retries=3,
      retry_filter=retry.retry_on_beam_io_error_filter)
  def delete_files(file_paths):
    """A function to clean up files or directories using ``FileSystems``.
  
    Glob is supported in file path and directories will be deleted recursively.
  
    Args:
      file_paths: A list of strings contains file paths or directories.
    """
    if len(file_paths) == 0:
      raise RuntimeError('Clean up failed. Invalid file path: %s.' %
                         file_paths)
    FileSystems.delete(file_paths)
  